By the middle of this century, nearly two-thirds of the world's population will be living in cities. If we want their lives to be pleasant, and the resources they use to be sustainable, urban development is going to have to change radically. That's the thesis of architect Rachel Armstrong, who works with synthetic biology to create prototypes of "living cities" built using biological materials. She imagines a future where cities aren't built, but instead grown like plants or baked like bread.

Over at the awesome Download the Universe blog, where we review ebooks about science, I've just posted a review of Armstrong's long essay, Living Architecture, about how these biological cities might work. Here's an excerpt:

Rooted in cutting edge biology and materials science, as well as contemporary art, Armstrong's account of how we'd build biological cities feels at first like a thought experiment but evolves into a plausible vision of tomorrow's cities.

The inspiration for the idea of biological cities comes from experimental architects, materials scientists, and synthetic biologists who are all coming to question the idea that a robust city is built like a machine. Now, it's beginning to seem that cities can also be grown like plants, or baked like bread. A lot of what's happening in architecture today, Armstrong explains, is based on the idea of "biomimicry," or designs inspired by nature. An installation called MUSCLE at Paris' Centre Pompidou demonstrated how a framework (for a house or piece of furniture) could respond to people's movements. Aside from biomimicry, there are simple ways to bring biology into traditional buildings, the way architect Patrick Blanc has done in his "living walls" of hydroponically-fed plants that stretch up the sides of train stations, museums, and more.

What's truly exciting about Armstrong's essay, however, is her research on "protocells," or cell-like chemical packages without DNA that can metabolize and transform other chemicals. These protocells, which can be manipulated to have a number of different features, have already been used to "heal" crumbling bricks by synthesizing limestone in the presence of water. And in a group project called Hylozoic Ground, which Armstrong works on, protocells have been used for carbon capture inside a biomimetic framework that moves and changes in response to the people walking through it.

Want to know what a city made with protocells would look like? Read the rest (and read some other reviews by my excellent co-editors) over at Download the Universe.